Scanning disk



Oct. 28, 1930. A. o. T TE 1,779Q51s SCANNING DISK Filed Dec. 13, 1928 [/VVENTOE dimensions.

It is well understood that the circumferen Patented Oct. 28, 1930 UNITED sr TEs ALFRED ORDE TATE, or TORONTO, ONTARIO, CANADA [SCANNING DISK Application filed December is, 1928. swarm. 325,874,.

This invention relates to improvements in scanning disks usedin the radial transmission of images, as described in the present specification and illustrated in the accompanying drawings whichform part of same.

The invention consists essentially of the novel features pointed out broadly and speeifically in the claims for novelty following a description containing an explanation in detail of anacceptable formof the invention.

The objects of the'invention are to ensure a clearly defined image; to eliminate diffused and blurred outlines; to reduce to a minimum confusion inthe darklines and shadows existing in the transmitted image; to ensure equalglight density throughout for the scanning of theimage; and generally, to provide a method of forming a'series of apertures in aiscanning disk capable of accomplishing the aforesaid results andpurposes.

It is to be noted that in the transmission of light through aperturesformed in a scanning disk, it is desirable that the volume of light transmitted through any aperture shall be the equivalent of that transmitted through any other aperture in the series which describes a spiral on the face of the disk. If

there be any variation in the relative values I .such tlnng aslateral motion which compreof these volumes, this difference will be expressed in thevolumes of, light reflected from the surface of the object which is being scanned, and, re-appearing in thelight utilized at the receiving end of the transmission system, will tend towards failure in the production of a faithful image of the original subject, i

This fundamental principle which comprehends the equalization of relative light values applies not only to the relative light values of a plurality of'apertures as arranged in a scanning disk to forma spiral, but relates also to the individual apertures themselves and in itsapplication controls and prescribes both their form and their relative tial speed of a revolving diskincreases progressively by unit radial measurement from centre to circumference and therefore that no two circumferential sections as defined at countered.

different points along a radial line are at any time equal with regard to their respec tive circumferential speeds. .in mind, it is obvious that when a round or cylindrical apertureis employed in-a revolving disk for the transmission :of light, the

Bearing this relative values of some of the groups of rays .which constitute the pencil passing therethrough are unequal with respect-to their relative. light values, one salient reason for this being that the upper half'of'such an aperture which in physical dimensions is the exact equivalent of the lower half, is passing the light source at higher speed than the latter, and must thereforetransmit a lesser Volume of light. Thereare other reasons for inequalities of light transmission in this form of aperture, which I shall discuss hereinafter. v 7' In the case ofa square aperture or any aperture wherein each of its four corners describes a right angle, inequalities similar to those described above must inevitably be en- Apertures of these two classes are adapted to transmit light in equal volumes through travelling mediums in which motion is expressed by lateral movement.

f In a revolving dis however, there is no hends a movement which with respect to any given point describes a straight line from side to side. The movement in a revolving disk is circular or circumferential and therefore the equalization of light values through a single or through a series ofapertures in such a diskinvo'lves conditions wholly divergent from those associated with lateral motion. There is onlyone method known to me by which the boundaries and therefore the form of an aperture in a revolving disk boundaries, two sections of the arcs of two circles which intersect the said radial lines and whose centres are identical with the centre of the disk. The space thus enclosed,

when formed as an aperture, will transmit a volume of, light equal in all its parts for the reason that all variations in circumferential speeds as expressed within the boundaries of the aperture itself have through its form been compensated for with mathematical precision.

With regard to a plurality of apertures arranged in series to form a. spiral and which starting with the first r outermost aperture, are fixed at progressively decreasing distances from the centre of the disk, each thus occupying space in a circumferential area different to that of any of the others and moving therefore at different circumferential speeds, it is obvious that to maintain equal light transmission values, no two apertures'can be of equal measurement with respect to the areas enclosed by their boundaries. These individual areas must be reduced in size to conform with the reductions indicated by the two converging radial lines which describe their side boundaries and intersect the two circles which constitute their top and bottom boundaries. By pursuing this method, the progressively decreasing dimensions of each aperture in a series constituting a spiral may be determined with mathematical precision, and it is only in this way that compensation can be effected for the varying surface speeds of a revolvin disk and equal relative light values se cured. I

Reverting now to the round or cylindrical aperture mentioned above, it is obvious that the arc of the circle forming its upper boundary does not and cannot be made to conform with the arc of the circumferential cir cle which is located at the same point and whose centre is identical with the centre of the disk. Again, the sides of this cylindrical aperture consist of two more sections of its own circle, instead of radial lines, while its bottom is the remaining fourth concave section of this circle instead of the convex section of a circle concentric with the centre of the disk.

The defects of a square aperture or of any aperture which fails to conform with the radial and radian measurements of the particular space which it occupies on the face of a revolving disk must now be obvious and it is not necessary that I should discuss them in further detail. I find that the most convenient and most accurate way to prepare adisk for the location of apertures as described herein is to devide it into 360 equal radial sections, or any multiple of 360 and again into concentric circumferential areas by means of circles spaced equally each from the other at any desired predetermined distance from the central axis of the disk, the centre of these circles being identical with the centre of the disk. Having done this, there will be defined on the face of the disk pluralities material.

of circumferential areas bounded at their sides by two adjacent radial lines and at top and bottom by the arcs of two circles. In the preparation of a scanning disk it is only necessary to select an initial 5 mm, thus defined, which conforms in area wit the predetermined sine of the light volume or pencil which is to be em oyed for surface scanning after which in t e lotting of the series constituting the spiral, t e correct areas with dimensions already defined, will be indicated and fixed by the spacings which represent the width of the surface of the object which is to be scanned.

In the drawin Figure 1 is a surface view of the scanning isk mode in accordance with this invention.

Referring to Figure 1, the numeral indicates a circular disk formed of any suitable The disk 10 is mounted at its central axis 11 on a shaft suitably rotated. The image to be scanned is indicated by the dotted lines at 12. 13 are apertures arranged in a. series to form a spiral in accordance with the usual procedure in arranging apertures in a. scanning disk. The outermost aperture 13A on the disk is adopted to scan the u permost portion of the image 12, while t e innermost aperture 138 in the series is adapted to scan the lowermost portion of the image 12. The disk 10 is divided into a number of equal sectom 14 by the radial lines 16 normal to the circumference of the didt. The disk is also divided into a number of concentric rings or zones 16, preferably of equal width, by the concentric circumferential lines 17. The boundaries of the apertures 13 are defined by the radial lines of the sector in which they lie and by the peripheral conuntriccireles 17 bounding the particnlarconcentric zone 16 in which the a rtuie is situated. The apertures are pref y spaced circumferentially from each other by a distance equal to or slight! greater than the width of the image 12, so t at only one aperture at a time will scan or re er on said image 12.

Commencing at t first aperture 13A. adjacent the periphery of the disk 1'0, ml! successive aperture in the series is situated in a successive concentric none crring 16 and more adjacent the central axis. The most convenient method of determining the boundary lines of each aperture in the series and its particular position in rega rd to the neighbouring apertures in said series is to divide the disk into radial divisions or sectors of equal radian measurement and into concentric circumferential divisions of equal width. As most images to be scanned are either square or rectangular in form, it will be noted that the uppermostportion of the image 12 will not cover oroccupy as may radial spaces or sectors its the lower pumice. Consequently, the apertures 13 more adjacent the theuiek will beopnoul from each other by a radial sectorof lesser radian measurement than the apertures more adjacent the central axis. The apertures are therefore spaced circumferentially from each other, according to the ninnber of radial di visions which are occupied by the image 12 in the particular zone in which the apertures are situated. In this case for'instance, as illustrated in Figure 1, in the outermost section, the image 12 occupies slightly more than five radial spaces. Thus the aperture 13A will be spaced from the following aperture in the series by six radial divisions 14. This spacing continues to the sixth aperture at 13C. s s f In the zone in which the next aperture 131) is situated, it will be noted that the image occupies six radial spaces, hence this aperture will be spaced from the preceding one in the series by seven radial spaces 14:. This spacing is continued until the aperture at 13E is reached. The aperture at 13E lies in a concentric zone in which the image occupies seven radial spaces, hence this particular aperture will be spaced from the preceding one by eight radial spaces. This spacing con-,

tinues until the final aperture 18B scanning the lowermost portion of the image 12v is reached.

It is to be noted that the apertures 13 could be spaced circumfe'rentially from each other by using a tool or spacer to determinethe width of the sector spacing any of the aper-,

tures in the series in accordance with their position with regard to the central axis 11. In other words, a tool or spacer may be used to so determine the position of the apertures that the circumferential distance between the first aperture 13A and the following one in the series is equal to the circumferential distance between the final aperturel3B and the preceding aperture or is equal to the circumferential distance between any one of' the apertures in the series.

The dimensions of the apertures 13 may be altered by changing either the width of the circumferentialzones or areas 16 or by altering the radian measurement of the sectorsl l, the peripheral boundaries of the zones 16 and the side boundaries of the sectors let, respectively determining the area or size of said apertures 13.

This invention in'operation serves to scan the image from top to bottom or bottom to top, according to'the direction of rotation of the disk, in successive sections similar to the scanning disks already in use in the radio transmission of the image of light reflecting bodies, but the apertures are so formed that equal light values are arrived at throughout the scanning area and transmitted therefrom to the scanned object, thus eliminating all confusion in transmission :due to unequal light values and ensuring the transmission. 0 a more clearly defined picture.

' WhatI claim-is: a

1. In a scanning disk for use in the transmission ofimages, a cirucuar disk mounted at its central axis on a shaft. suitably rotated,

arcual divisions of equal radian measurement formed on the face of the disk by radial lines through the central axis of saidvdisk and cir I 2. In a scanning disk for use in thetransmission-of images, a circular disk mounted at its centralaxis on a shaft suitably rotated,

a plurality of arcual apertures formed there through and in a series arranged in a spiral commencing adjacent the periphery of said disk and ending at a point more adjacent to the central axis thereof, said aperturesbeing spaced circumferentially from each other by a distance at least as great asthe width of the image torbe scanned and so spaced in respect to the central axis of said disk that each succeeding aperture'in the series will scan a successive portion of said image and said disk and by circles concentric with said central axis.

'3. The method of forming, and arranging -apertures in a scanning disk viding the face of said disk into a plurality of arcual spacesby radial lines equally spaced circumferentially from each other and passing through the central axis of said disk, and by concentric circles equally spaced from each other and concentric with said central axis, and the forming of said aperturesbounded by said radial lines and by said having their respective boundaries defined .b'y radlal lines through the central axis of for use in the transmission of lmages, consisting of sub-diconcentric circles in certain of-said arcual spaces atvarying distances from the central axis of said disk and spaced circumferentially from each other by substantially equal distances.

4. The method of. forming and arranging apertures in a scanning disk for use in the transmission" of images'consisting of forming the apertures with their side boundaries de fined by radial lines passing through the central axis of said disk and so spaced circumferentially that the radian measurement of all of said apertures will be equal, and with the boundaries adjacent to and distant from saidcentral axis defined by circumferential I line s concentric with said central axis, said apertures being spaced circumferentially by a distance at least as great as the width of the image to be scanned and placedin relation to the central axis of said disk in such a manner that each succeeding aperture will scan a succeeding portion of theimage until the whole of said image has been scanned in one revolution of said disk.

5. A scanning disk for use in the transmission of images, said disk having apertures arranged in a series and spaced circumferent-ially from each other by a distance at least as great as the width of the image to be scanned and situated at varying distances from the central axis of said disk, said apertures having areas which vary directly as the distance of the individual aperture from the center of said disk.

6. A scanning disk for use in the transmission of images, said disk having apertures arranged in a series and spaced circumferentially from each other by a distance at least as great as the width of the image to be scanned and situated at varying distances from the central axis of said disk, said apertures being formed progressively larger as they progress from the center of said disk to the circumference thereof.

71A scanning disk for use in the transmission of images, said disk having apertures arranged in a series and spaced circumferentially from each other by a distance at least as great as the width of the image to be scanned and situated at varying distances from the central axis of said disk, all of said apertures being of equal radial dimensions and said apertures having a circumferential dimension which varies directly as the distance of the individual aperture from the center of the disk.

8. In the method of scanning an image by passing a ray of li ht through apertures traveling at varying speeds, the improved step which comprises forming said apertures so that the area of the individual apertures is directly proportional to the speed of movement thereof, whereby the total quantity of light applied by each aperture to the image substantially equal.

9. In the method of scanning an image by passing a ray of light through a plurality of apertures traveling at difi'erent speeds, the improved step which comprises forming said apertures of different dimensions in the direction of travel thereof, said, dimensions being such that the length ofeach aperture is directly proportional to the speed of travel thereof, whereby the total quantity of light applied to the image by each, of said apertures is equal.

10. In a scanning apparatus, an element having apertures, the area of each of said apertures being directly proportional to the speed of travel thereof.

11. In a scanning apparatus, means for scanning an image including a plurality of apertures traveling at different speeds, said apertures being of the same dimension in the direction transverse to their line of travel and of varying dimension in their line of travel, said dimension in the line of travel of the aperture being proportional to the speed of travel thereof.

Signed at the city of Toronto, this 5th day of December, 1928.

ALFRED ORDE TATE. 

